The effectiveness of solid form pesticides is dependent not only upon the active ingredient but also upon the inert ingredient used as the carrier for the active. The inert carrier acts as the transfer mechanism for the active ingredient. If the carrier does not effectively release the active, the active will never reach its intended target. Thus, the development of an effective carrier is an essential step in the development of a successful pesticide.
To be of optimum effectiveness, a carrier must release its active in sufficient quantities such that the environment of the targeted site maintains the minimum concentration level needed for the active's intended use. If the concentration of the active falls below this minimum, it will cease to be effective. If the carrier releases the active too quickly, several problems can occur. First, the concentration level in the surrounding environment can exceed certain minimum safety standards. When this happens, unacceptable hazards can arise. Secondly, if the carrier releases the active ingredient in amounts in excess of what is needed, the carrier will deplete itself in a shorter amount of time. In addition, some actives break down and become inactive in a relatively short period of time when subjected to hydrolysis and photolysis and therefore should not be released too quickly. As a result, there can be an overall reduction in the effective life of the pesticide, which in turn, means more frequent applications.
Some carriers currently exhibit quick release characteristics but do not supply long-term control. Conversely, other carriers which provide long-term control are not capable of producing an initial quick response. Thus, the only way to vary the control of the product is to vary the application rate. For example, to achieve a quick response with a slow release product involves increasing the initial application rate, which in turn actually wastes the active ingredient since the long-term effect will be extended beyond the initially desired period of control.
To help reduce these problems, the Applicant has invented an improved carrier which allows for controlled release of the active ingredient in a desired pattern. This is achieved by combining preselected quantities and sizes of varying corncob fractions which exhibit different release rates. By combining cob fractions in a preselected manner, a carrier can be designed which can have a slow release rate, a fast release rate or a combination of the two.
Dow Chemical previously produced a product known as Dursban 10CR which allowed the controlled release of an active by impregnating a plastic pellet with the active. One of the drawbacks to this prior art product was that the pellet was not quickly biodegradable and would therefore remain in the environment for quite some time. This product is no longer marketed.
It is an object of the present invention to provide a carrier which, when treated with a particular active ingredient, will provide an effective mechanism for releasing the active ingredient in a predetermined and desired pattern. It is also an object of the present invention to provide such a carrier which allows controlled variations in the slow and quick release concentrations of the active ingredient. It is a further object of the present invention to provide such a carrier which has an organic composition which will act as a bait when exposed to certain target organisms and which biodegrades.
Other objects and advantages of the present invention will be apparent from a review of the following specification, tables and graphs.